The present invention generally relates to electricity generating devices, and in particular, to an electricity generating device that generates electricity by gradually extracting mechanical energy stored in a flat spiral spring such as a power spring and supplies the extracted energy to an external circuit and to a method for controlling such an electricity generating device.
One type of conventional electricity generating device is described in the Japanese Patent Public Disclosure No. 5-284690/1993 Official Gazette. This conventional device includes a power-spring battery that can transform the mechanical energy of a power spring into electric energy by means of a generator or dynamo and can transmit an electric current to an external electrical device. The electric current has the form of a pulsating current, which has a level varying within a predetermined amplitude or voltage and is obtained by using a three-terminal regulator and a capacitor. A second conventional electricity generating device, described in the Japanese Patent Public Disclosure No. 59-135388/1984 Official Gazette, is a clock which can measure an elapsed time with high accuracy by controlling the number of rotations of a generator or dynamo driven by a power spring, by means of an oscillator such as a crystal.
These conventional electricity generating devices, which generate electricity by using energy stored in power springs, may be effective in handling every day electric and electronic equipment in geographic regions that do not have power transmission networks. Further, in the aforementioned electronic generators, electric power can be obtained by periodically winding up the power springs thereby reducing the fear that the batteries may run down. Therefore, these conventional electronic generators can serve well as a backup power source during a disaster, such as an earthquake.
However, in a conventional power-spring battery, the smaller the power consumption of the electric equipment to be supplied with electric power becomes, the more ineffectual an electromagnetic brake is rendered. Thus, if the power consumption of such electric equipment is small, the generator or dynamo rotates at a high speed and the power spring is unwound quickly. Moreover, in the case where no electric equipment is connected to the conventional power-spring battery, the power spring is unwound rapidly. Consequently, the conventional power-spring battery can not function as a battery.
Furthermore, if, for example, the conventional power-spring battery is connected to an electric device such as a portable telephone which requires varying power consumption depending upon, for example, whether the telephone is in a reception wait state or in a busy state, the battery must generate electricity to maintain a state requiring the maximum working power, and the battery will supply more energy to the device than the device may require. The conventional power-spring battery, therefore, does not maximize the energy stored in the power spring. Moreover, most energy supplied from the power spring to the generator or dynamo is lost due to magnetic and mechanical causes such as air resistance. Consequently, when using the conventional power-spring battery, an electricity generating device having a sufficient lifetime can not be achieved.
Accordingly, an electricity generating device, which can effectively utilize energy stored in a power spring, can control electric power in accordance with the power consumption required by the external circuit, can automatically minimize the energy used to drive a generator or dynamo in accordance with the amount of electric power used by the external electric equipment and which has a wide range of an amount of electric power to be used and has a long lifetime, is desired.